docs: def plot_ellipse_matplotlib(cov, pos, ax, nstd=2, **kwargs):
      """
      Plot 2d ellipse in 3d using matplotlib backend
      """
      from matplotlib.patches import Ellipse
      from mpl_toolkits.mplot3d import art3d, Axes3D
      ellipse_param, normal = calc_2d_ellipse_properties(cov,nstd)
      ellipse_kwds = merge_keywords(ellipse_param, kwargs)
      ellip = Ellipse(xy=(0,0), **ellipse_kwds)
      ax.add_patch(ellip)
  
      ellip = pathpatch_2d_to_3d(ellip, normal=normal)
      ellip = pathpatch_translate(ellip,pos)
      return ellip